Change transparency of image on map layer?

Hi,

I have a regular map on my map layer and would like to add a second image on top and make it transparent. Is this somehow possible or do i need to add the transparency before and upload it as a png?

for excample id like to use a gif of moving fog all over the map. but the gif itself is not transparent. So id just like to change the opacity of the token.

Cheers

Tobi

You are correct in surmising that you would need to adjust the transparency before uploading. Roll20 can adjust the transparency of auras and objects created by the drawing tools, but has no such controls for images.